Wattmeter-testing apparatus.



PATENTED APR. 28, 1908.

0. A. KNOPP. WATTMETER TESTING APPARATUS.

APPLICATION FILED JUNE 19,1907.

l creasing may be installed; it being PATENT OFFICE,

OTTO A. KNOPP, OAKLAND, CALIFORNIA.

WATTMETER-TESTING APPARATUS.

' Application filed June 19,

To all whom it may concern:

Be it known that I, OTTo A. KNoPP, a sub-' ject of the Emperor ofGermany, residing in Oakland, California, have invented certainImprovements in Wattmeter-Testing Apparatus, of which the following is aspecification. a One object of my invention is to provide a compactassemblage of apparatus particu larly designed and connected to providea convenient means for testing recording wattmeters without thenecessity for removing them from the various positions in which theyfurther desired that the apparatus shall be of such anature as to beconveniently portable. In addition, it is desired to provide a wattmetertesting set, which, though consisting of but relatively few pieces ofapparatus, shall be capable of testing wattmeters of widely rangingcapacities and under widely varying loads, in order to properlycalibrate them to ascertain their condition or accuracy. These objectsand other advantageous ends I secure as hereinafter setforth,reference'being had to the accompanying drawing, in which ;the figure isa diagrammatic representation of the apparatus comprising my improvedtesting set.

g In the above drawing, A'and A represent the terminals of the device,which it will be understood are connected to any. desired source ofcurrent, while B represents a wattmeter to-be tested. This latter isrovided with a current coil 6 through whic under service conditions,passes the current to be measured'and in-addition there is a potentialcoil 6 connected across the current supply mains, but in series with avariable regulating resistance 0. This resistance while being capable ofvariation in any of the ways well known to the art, in'the presentinstance is illustrated as having its coil so arranged that the amountof resistance in circuit may be varied by shifting the position of asliding arm 0; it being noted that the Wire constituting this resistanceis preferably made 'of incurrent carr g capacity, from the point a atthe ends-of the two bodies of resistance shown, toward the two points aand 0 I which latter are so'connected as to-permit the sliding arm 0 toshort circuit the entire body of resistance Owhen they aresimultaneously engaged by said arm 0." The first of the points 0 or oneend of the resistance coil O, is

' connected to the current supply main A,

Specification of Letters Patent.

Iatented April 28,1908. 1907. Serial No. 379,783. I i

I while the terminal c is connected to the movable arm (1 of a two-pointswitch D. One of the terminals d of this switch is connected through astandard resistance unit eiand an ammeter E to one end of the currentcoil 6 of the'wattmeter, B; the other end of this coil being connectedto the current ,supply main A. a A second standard resistance unit 6 hasone end connected to the terminal d ofthe switch D and its second endconnected through a switch 6 to that portion of the connection whichextends between the ammeter E and the current coil of the wattmeter. Thesecond terminal d of the switch D is connected to a'conductor extendingbetween the standard resistance unit e and the switch 22 In addition tothe above, I -provide any desired number of. resistance units (in theesent instance three,indicated at F, F and each consisting of and Iconnect'these coils with switches G and in such manner that any of thecoils f two sections f an f resistance coil 6 and the ammeter E by promanipulation of the switch Similar by suitably manipulatingithe switch Gany oneof theentire resistance units F, F or'F may be thrown in parallelwith the two resistance units 1; and e connected in series with eachother and-with the ammeter E. Under operatingconditions, it' is obviousthat if. the sliding arm ofthe variable resistance C be placed tocompletely out out said "resistance, and the i switch arm d be placed incontact with either of the points (1 or (1 while the switches G, G and ea certain definite and fixed voltage will cause a certain-current toflow and be indicated on the ammeter E.

Assuming that the arm belin eng ment with the point d of the switch Dand indicationof the ammeter, in addition todirectly giving the amountof on ent flowing in the circuit, and, therefore, t '011 h the currentcoil 6 of the the well known calculation,give thevoltag'e causing suchflow of current. From these two quantities it is now'possible todetermine the watts of the circuit once calibrate the Wattmeter B forthis load,

as determined by the standard resistance. The variable resistance A thepoint of that the resistance of the coil e is known, the

and,"therefc'n'e, to at singlecoil e of the are open,

age-- wattmet'er, will a so, by

v the switchD and the potential coild may, if

4 meter any one of the coils f,

desired, be varied in order to bring the voltage applied to thewattmeter and the other apparatus concerned in the testing circuit, toan desired figure.

n order to vary the load upon the wattof the units F, F and F maybethrown into. parallel with the coil e and the ammeter E by placing theplug of switch G in the proper recesses; it eing understood that thesevarious coils are of different but predetermined and standardresistance.

It will be seen that the plugging into the circuit of the coils f doesnot increase the current flowing through the coil e and the ammeter E,but merely serves to increase the value of the scale reading on theannneter by causing additional current to flow through the wattmeter.With the switch G open, the lead on the, wattmeter may be furtherincreased by closing the switch 6 inasmuch as this laces the coil 6 inparallel with the coil e anf the ammeter E, and if with this arrangementthe various ones of the coils f be thrown into circuit, acorrespondingly increased number of different loads is placed upon thewattmeter B.

Should it be desired to test a wattmeter adapted to o erate at a highervoltage than that for whic i the coils f and e are desi ned, then thearm (1 of the switch D may be p aced in engagement with the terminal (1it being understood that the switches e and G are open under theseconditions. This arrangement of connections places the coil e in serieswith the coil e and with the ammeter E, and if the switch G be properlymanipulated, it will be seen that any one of the resistance units F, For F may be thrown in parallel with the entire resistance unit E and theammeter, as before giving a wide range of load variation to thewattmeter.

It will be understood that the standard resistance units have atemperature coeflicient of zero and under commercial conditions are soro ortioned that the ap aratus is used wit 1 t e arm 05 of the switc Din engagementwith the contact point (1 on a 110 volt circu'it'and withthe arm on the contact (1 on a 220 volt circuit.

1. A wattmeter testing set including a twooint switch connected to onecurrent supp y main, a standard resistance unit having two sections, anammeter having one terminal connected to one of said sections and asecond terminal connected to the wattmeter to be tested, and a secondswitch connected between one of the points of the first switch and theconnection between the wattmeter and the ammeter, both sections' of theresistanceunit being connected to the second point of the twoointswitch, and the sec and section of sai resistance unit being connectedbetween the first point of said switch and the second switch,substantially as dee scribed.

2. A wattmeter testing setincluding a standard resistance unit havingtwo sections, an ammeter, a twooint switch, and a single point switch,wit connections between said apparatus arranged to permit of said tworesistance sections being connected both in series with the ammeter, onein series with the annneter and the other in parallel with the ammeterand the first section, or one of said sections in series with theammeter, substantially as described.

3. A wattmeter testing set including a two-point switch, a standardresistance unit having one section connected between the two contactpoints of said switch and a second section having one end connected toone of the contacts of said switch, an ammeter in series with saidsecond section, with a connect-ion between said ammeter and thewattmeter to be tested, and a switch for connect.- ing the two sectionsof the resistance in par allel with each other, substantially asdescribed.

4. A wattmeter testing set including a two-point switch, a standardresistance unit having two sections, a plurality of standard shuntresistances also each having two sections, an ammeter in series with oneof the sections of the standard resistance unit, means for placing onesection of any one of the shunt resistances in parallel with one of thesections of the standard resistance and the ammeter, and means forplacing both sections of any one of the shunt resistances in parallelwith both sections of the standard resistance unit connected in serieswith each other and with the ammeter, substantially as described.

5. The combination of a two-point switch,

two multi le point'switches, a plurality .of bodies of s unt resistanceconnected to said multiple point switches, a body of standard resistancehaving two sections, one of the sections being connected between thecontacts of the two-point switch, an ammeter in series with the othersection, and connections whereby any one of the shunt resistances may beconnected as a wholejn parallel to the two sections of the standardresistance connected in series with each other and with the ammeter,said connections also permitting one section of any of the shuntresistances being connected in parallel with one of the sections of-thestandard resistance, substantially as described.

In testimony whereof, I have signed my name to this specification, inthe presence of two subscribing witnesses. 'OTTO A. KNOPP.

Witnesses:

H. A. LUTTRELL, J. C. PINKERTON.

